The invention relates to a bolt or lock mounting for fitting on both sides of a panel or wall comprising a circular orifice extended by a plurality of substantially rectangular cut-away portions disposed crosswise.
The strength of bolts mounted on relatively thin walls, as is the case for example with automobile doors, is directly connected to the fixing method utilised.
It is usual for a circular opening extended by cut-away portions disposed crosswise to be formed in the wall and for a corresponding form to be imparted to the external part of the bolt mounting which passes through the wall, the mounting being retained by a fork piece on the face of the wall which is not accessible. The co-operation of the profiled part of the mounting with the cut-away of like form of the wall prevents rotation of the fixed part of the bolt mounting.
However in the case of an attempt at violent twisting, the resistance offered by the wall is often insufficient by reason of the fact that it works directly to buckling in the weakened zone of the opening. Likewise the resistance to driving-in is often insufficient.